Synthesis and characterization of a series of cross-linked polyamines for removal of Erichrome Black T from aqueous solution

Abstract

• Synthesis of four cross-linked terpolymers by one-step polymerization method. • Characterization of the polymers by various techniques. • High EBT adsorption capacities of 775 mg/g and 917 mg/g by two polymers. • Equilibrium, kinetic and Thermodynamics studies. • Polymers show promising reusability. A new series of polymers comprising four terpolymers was synthesized via Mannich polycondensation of benzene-1,4-diamine, formaldehyde and piperazine by varying the benzene-1,4-diamine and piperazine ratio. The new polyamines (labeled Dipip) were characterized using 13 C solid-state NMR, FT-IR, TGA, DSC, XRD, SEM and EDX. The adsorptive performances of the synthesized polymers for Erichrome Black T (EBT) uptake from aqueous solution were investigated under batch process. Equilibrium, kinetic, and thermodynamic studies were conducted to determine the influence of different operational parameters of the adsorption process. The two most promising polymers among the series show an excellent EBT removal efficiency of ~100% and ~95% with high adsorption capacities of 775 mg·g −1 and 917 mg·g −1 , respectively at a meager dosage of 5 mg. The sorption of EBT on the polymers was well described by Redlich-Peterson & Langmuir model while the kinetic studies indicate that pseudo-second order model was followed. For the thermodynamic studies, the negative Δ G and positive Δ H values obtained suggest a spontaneity of the sorption process which was endothermic in nature. The results of reusability test of the resins were promising even at the fourth cycle, showcasing the potentials of the new polymers in dyes contaminated water treatment.